An OTN (optical transport network, optical transport network), as a core technology of a next-generation transport network, includes technical specifications at an electrical processing layer and an optical processing layer, has OAM (operation, administration and maintenance, operation, administration and maintenance), TCM (Tandem Connection Monitoring, tandem connection monitoring) and out-of-band FEC (forward error correction, forward error correction) capabilities, is capable of achieving flexible scheduling and management of large-capacity services, and gradually becomes a mainstream technology for a backbone transport network. At the electrical processing layer, a “digital wrapper” structure defined by the OTN technology can implement management and monitoring on a client signal.
As shown in FIG. 1, an OTN frame is a 4080×4 modular structure, including a frame alignment signal (frame alignment signal, FAS) byte, which provides a function for locating the OTN frame. An OTUk OH (optical channel transport unit-k overhead, OTUk overhead) is overhead bytes of an optical channel transport unit, which provides a network management function at an optical channel transport unit level. An ODUk OH (optical channel data unit-k overhead, ODUk overhead) is overhead bytes of an optical channel data unit, which provides a maintenance and operation function. An OPUk OH (optical channel payload unit-k overhead, OPUk overhead) is overhead bytes of an optical channel payload unit, which provides a client signal adapting function. An OPUk (optical channel payload unit-k) is the optical channel payload unit, which is used for carrying a client signal. An FEC (forward error correction) is forward error correction bytes, which provides an error detection and correction function. A coefficient k indicates a supported bit rate and different types of OPUk, ODUk, and OTUk. k=1 indicates that a bit rate rank is 2.5 Gbit/s; k=2 indicates that a bit rate rank is 10 Gbit/s; k=3 indicates that a bit rate rank is 40 Gbit/s; k=4 indicates that a bit rate rank is 100 Gbit/s; and k=flex indicates an any-rate bit rate. An ODUflex frame specified by ITU-T is capable of carrying an any-rate CBR (constant bit rate, constant bit rate) service and a packet service.
Presently, a 100GE standard 802.3ba and an OTN OTU4 (100 Gbit/s) standard G709v3 have been completed. However, with rapid growth of services, an ultra-100GE (such as 400GE and 1TE) service is ready; to meet service transport requirements, a transport solution of a corresponding rate level needs to be made at the optical transport layer; for example, an OTU5 (400 Gbit/s) is defined to transport a 400GE service and achieve a long-distance transmission over a 400G WDM optical module. Further, because spectral efficiency has a limit, a rate of an optical transport module is difficult to increase infinitely. Presently, the utilization of spectrum efficiency by a long-distance WDM optical module at a rate level of 100 Gbit/s has been close to a limit, to continue evolution of a 100 Gbit/s network, considering technical feasibility, an ultra-100 Gbit/s transport network will adopt a 400 Gbit/s long-distance WDM optical module. With rapid growth of services, such as the emerging of 400GE and 1TE services, these large-capacity services exceed a current single-wavelength transport capability of a transport network, and therefore, a preferable optical transport solution needs to be made under existing conditions to solve an actual problem of transporting an ultra-high-speed Ethernet service (such as 400GE and 1TE) in an OTN.